Sound transmission.



S. I. PRESCOTT.

SOUND TRANSMISSION.

APPLmATIoN rum) MAR. 18, 1909.

965,327. v Patented July 26,1910.

SYDNEY I. PRESCOTT, OF CAMDEN, NEW JERSEY.

SOU1 TD TRANSMISSION.

Specification of Letters Patent.

Patented July 26, 1910.

Application filed March 18, 1909. Serial No. 484,283.

To all whom it may concern:

Be it known that I, SYDNEY I. PREscoTT, a citizen of the United States, residing at Camden, county of Camden, in the State of New Jersey, Improvement in Sound Transmission, of which the following is a specification.

This invention relates to an improvement in soundtransmission, particularly to sound transmission as applied in the art of recording sound.

It is well known that sound in passing from one medium to another, or in passing from one stratum to another of the same medium, is refracted and that the propagation of the sound wave is, in consequence, interrupted, and in some instances the sound is destroyed. When air is the medium through which the sound travels, a column of heated or otherwise disturbed air occupying a position in the path of the travel of the sound wave forms an acoustic cloud which interrupts the uniform propagation of the sound wave, in some instances deflecting it so that an aerial echo is produced. The presence of these or other disturbances in the air makes the same non-homogeneous and not in the condition best adapted for a uniform propagation of sound waves. In the art of re cording sound itis very desirable that the sound be recorded in its initial purity. This cannot be accomplished if the sound is caused to travel through air which is nonhomogeneous.

It is one of the objects of the present invention, therefore, to provide means for maintaining the air between the source of sound and the receiver in homogeneity, so that there will be no alteration in the sound, which is detrimental to the same, between the source of sound and receiver, or recording instrument.

In recording sound, as at present practiced, great care is necessary in positioning the source of sound and in positioning the sources of sound, where a plurality is used, in order to attain the desired result. In

other words, where the tones of different voices are to be recorded the position of the singers with respect to the conductor and recording instrument, must be different, and in many instances aspecial sound conductor must be used for a' articular voice, otherwise imperfect recording will result. So, in the recording of instrumental music, the position of the different instruments must be have invented a new and useful .carefully considered and even then s ecial skill is required of the musicians and the recording operator. Furthermore, in the present practice of recording selections which include the tones of the human voice with an accompaniment of one or more instruments, it is necessary for the singer to be positioned much nearer the recording instrument than the accompanying instrument or orchestra. It is. usual in such cases to utilize difi'erent sound conductors for the singer and the orchestra, the result being that there is no combination of the two sets of sound waves until just before the waves reach the recording instrument or receiver. In singing in an auditorium the singer is usually at a greater distance from the audience than the orchestra, but in all cases before the two sets of sound waves reach the audience they have been thoroughly superposed and combined and the wave reaching the audience is a superposed or combine wave in which, however, the distinct characteristics of the original sound waves have not been destroyed. No such action takes place in the present method of recording. The element of distance which is essential to effect the true combination of the two sets of waves is entirely absent. In the art of recording sound it is highly desirable that the sound recorded possesses the same characteristics as the same sound heard by an audience in an auditorium.

It is one of the objects of this invention, therefore to provide means whereby the several sound waves aresuperposed and c0m bined in the same way that they are in an auditorium.

The tympanum of the human ear is much more sensitivethan a recording instrument and consequently the former will receive as a clear impression a much smaller portion of the sound Wave propagated than a recording instrument. In other words, it is necessary in the art of recording sound to utilize a larger portion of the sound wave than that which will produce a clear impression upon the auditory system.

Owing to the fact that a very small portion of the sound wave does not possess sufficient power to operate the recording instrument, it is another object of the present invention to provide means whereby a relatively large portion of the sound wave, or sound waves, is concentrated atsa predetermined point with respect to the receiver, so

that there will be suflicient power in theselected portion of the Wave to eifectively operate the recording instrument.

A further object of the present invention is to provide means for regulating the temperature of the air through which the sound travels in order to maintain it in homogeneity.

Heretofore, it has been found almost, if not quite, impossible, to record sound in the open air. This is due to the fact that the air is not in a homogeneous condition and is affected by the wind, which in itself oftentimes forms an acoustic cloud and other causes of disturbance.

It is a further object of the present invention, therefore, to provide a chamber free from such disturbances across which the sound travels and in which the air is maintained in a homogeneous condition.

Heretofore, considerable trouble has been experienced in recording sound in rooms rectangular or substantially rectangular in form. In such rooms sound crashes and di rect echoes are frequently produced, and both detract from the purity of the initial sound, and in some instances prevent recording entirely. Various means have been employed in attempts to overcome the defects of .the recording rooms, but none of these rooms are acoustically perfect.

It is another object of'the present invention, therefore, to provide a chamber substantially ovoidal in form wherein the formation of sound crashes and echoes is impossible. The entire sound wave produced cannot,

in any case, be recorded.

It is a' further object of the present invention, therefore, to provide a chamber having a sound-absorbin g surface or wall which will absorb or destroy a portion of the sound wave propagated; that is to say, that portion of the sound wave which is not utilized for recording purposes, is absorbed so that it will not interfere with the selected portion recorded.

With these and other objects, not specifically-mentioned, in view, the invention consist-s in certain combinations and constructions, which will be hereinafter fully described and then specifically set forth in the claims hereunto appended.

In the accompanying drawings which form a part of this specification and in whichlike characters of reference indicate the same parts, Figure 1 is a sectional plan view of a device constructed in accordance with the invention; Fig. 2 is a longitudinal sectional elevation of the device illustrated in Fig. 1; and Fig. 3 is a cross sectional view.

In carrying the invention into efiect there is provided a receiver for the sound, and this receiver may vary within wide limits.

1 v 4 While in some constructions the receiver may constitute an element of the recording instrument, in the best constructions, and as shown, a receiver 1 is provided which acts not only as a receiver for the sound but also as a conductor by means of which the sound is conducted to a recording instrument. In the drawings, the recording instrument is not shown because the details of the construction of the same lies entirely outside the range of the present invention and its illustration is deemed unnecessary to an understanding of the same, and 1s,

therefore, omitted in the interest of brevity and clearness. In the drawings, however, the X marked 2 indicates the position of the impulse receiving element of a recording instrument.

There is provided a source of sound or sources of sound, indicated by X X at 1n the drawing. The source or sources of .soundindicate the position of a singer, or

an orchestra, or both. When a plurality of sources of sound are used for recording purposes, as for instance, when a song with an orchestral accompaniment is to be recorded, it is necessary that the sound waves propagated from the various sources of sound be superposed and thoroughly combined without destroying thevdistinct characteristics of .each, before they reach the receiver, so that the recorded sound will be the same sound that is heard under like conditions in an auditorium. T 0 effect this combination it is necessary that time be allowed for the sound waves to become superposed and fully combined. In the best constructions, therefore, the sources of sound will be spaced a considerable distance from I the receiver 1 before referred to.

It is well known that a recording instrument is less sensitive than the tympanum of the human ear and that, therefore, a relatively large portion of the sound wave, or sound waves, must be utilized when the sound is to be recorded. Owingto the fact that the source or sources of sound and the recelver must be spaced apart a considerable distance and that the area of the receiver is relatively small with respect to the sound wave at a distance from the source or sources of sound, and that at this distance the smaller portion of the sound wave which reaches the receiver will not have sufficient power to operate the'recording instrument, it is necessary that means be provided for bringing the recording instrument under the influence of a larger portion of the sound wave, or sound waves, than that which would reach it during the natural propagation of the wave. Means are provided,therefore, for causing the concentration of a'portion of the sound wave at a predetermined position with respect to the receiver, and

this means may vary within wide limits.

2Q gation of sound waves may be interrupted between the sources of sound and the relimits.

same is In the best constructions, however, this means will not only cause the concentration of a portion of the sound wave, but of a predetermined selected portion of the sound wave at a predetermined position with respect to the receiver. As shown, this means will cause the concentration of a portion of the sound Wave at a point marked C lying between the source of sound and the receiver, although it is to be. understoodthat in some constructions the point-of concentration might be otherwise located, as for instance, within the receiver. In the best constructions, the .means for causing the concentration of a portion of the sound wave consists in a deflecting surface 3 mounted behind and above the sources of sound S before referred to.

It is well known that the uniform propaby acoustic clouds and that acoustic clouds may be formed by air currents, whether produced by heat or pressure, and various other disturbances. Owing to the fact that the source of sound and the receiver are spaced apart and that the sound waves must pass through the intervening air, it is necessary in order to insure that an uninterrupted sound wave be recorded, that disturbances of the air between the sources of sound and the receiver be prevented. Means are provided, therefore, for maintaining the air through which the sound travels in homogeneity; that is to say, means are provided or preventing any disturbances in the air ceiver from interfering with the even propagation and concentration of the sound waves. This means may vary within wide lVhile other means may, in'some constructions, be provided for maintaining the air through which the sound travels in homogeneity, in certain constructions this means will include means for regulating the temperature .of the air so that no acoustic clouds will be formed by heated air currents between the sources of sound and the receiver. When air regulating means are used, this means will, in the best construc tions, be of such a character that it will also prevent any Wind disturbances in the'air between the sources of sound and the receiver. As shown, the sources of sound are located within a chamber 4, the walls of which will prevent any wind disturbances. For the purpose of regulating the temperature of the air within 'the chamber 4, the floor of the provided with a series of hot-air ducts 5 communicating with a hot-air cham- The hot-air the chamber between the source or sources of sound and the receiver. the chamber is provided with a series of cold-air ducts 7 each in communication with wave not selected and The ceiling of a cold-air chamber 8 located above the ceiling. It will be readily understood that hotair entering the chamber at the floor through the ducts 5 will silently rise toward the ceiling, and it will also be readily understood that cold-air entering through the ducts 7 in the ceiling will silently descend toward the floor and that an oven temperature in all parts of the chamber will thereby be maintained. It will be further understood that the air within the chamber between the source or sources of sound and the receiver will be free from all air currents of a nature to interrupt the propagation of the sound Waves.

When sound is transmitted through the air in a rectangular or substantially rectangular chamber or room, it is well known that sound crashes and echoes are produced at the corners thereof. It is further well known that these sound crashes and echoes interfere seriously with the recording of the initial sound, because the crashes as well as the initial sound are recorded. Means are provided, therefore, for preventing the formation of sound crashes and echoes. In the best constructions, the desired result is effected by making the chamber 4 substantially ovoidal in form, as shown, so that there are no corners to produce sound crashes and no flat surfaces against which the sound strikes to produce echoes.

It is well known that the entire sound wave cannot be recorded and that that portion of the sound wave which is not reoorded must be effectually disposed of so that it will not interfere with the selected portion to be recorded. To effect this result, in the best constructions the chamber 4 is provided with a sound-absorbing surface 9 which includes the entire surface of the chamber, except the deflecting surface 3, before referred to. This sound-absorbing surface may be constructed in a manner well known to architects. It will be readily understood that that portion ofthe sound deflected by the'defleeting surface 3 will reach the sound-absorbing surface 9 of the chamber and be there absorbed so that there will be no interference with the concentration of the sound wave at the point of concentration C.

From an inspection of the drawings, it will be readily understood that the sources of sound occupy a position within the chamber, and are located at the smaller end thereof, and that the receiver 1 is located in the Wall of the chamber opposite the sources of sound or at the larger end of the chamber, although it is to be understood that the relative positions of the sources of sound and the receiver with respect to the chamber may in some constructions be varied.

There must be light within the chamber.

his undesirable for acoustic reasons to interrupt either the deflecting surface 3 or the absorbing s rface 9 by piercing them I the heat from this lighting means interfering with windows, f r the glass of the window would form a deflecting surface which would produce an interference with the sound Waves. Means are provided, therefore, for lighting the chamber, and in order to prevent with the concentration of the sound wave, the lighting means for the chamber will be located beyond the range of action of the concentrating means, in the best constructions at opposite sides of the chamber, position of the lights being indicated by the crosses 10. It will be readily understood that the heat from these lights will rise close to the absorbing wall 9 where it cannot interfere with the main sound wave.

, In view of the foregoing, a detailed description of the operation of the device is deemed unnecessary, and is, therefore, omitted in the interest of brevity and clearness.

Changes and variations may be made in the structure by means of which the in- 2. The comblnatlon wlth a source of sound, of a receiver, means for causing the concentration of a predetermined selected portion of the sound wave at a predetermined position with respect to the receiver, and means for maintaimng the air through which the sound travels in homogeneity, substantially as described.

3. The comblnation with a source of sound, of a receiver, means for causing the concentration of a portion ofthe sound wave at a position between the source of sound and the receiver, and means for maintaining the air through which the sound travels in V homogeneity, substantially as described.

4. The combination with a source of sound, of a receiver, means for causing the concentration of a predetermined selected vportlon of the sound wave at a os1t1on between the source of sound and t e receiver,

and means for maintaining the air through which the sound travels in homogeneity,-

substantially as described.

5-. The combination. with a plurality of the sources of sound, of a receiver, means for causing the combination and concentration of portions of the sound waves at a predetermined position with respect to the receiver, and means for maintaining the air through which the sound travels in homogeneity, substantially as described.

6. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of predetermined selected portions of the sound waves at a predetermined position with respect to the receiver, and means for maintaining the air through which the sound travels in homogeneity, substantially as described. V

7. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of portions of the sound waves at a position between the sources of sound and the receiver, and means for maintaining the. air

through which the sound travels in ho-' mogeneity,substantially as described.'

8. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of ?predetermined selected portions of the sound waves ata position between the sources of sound and the receiver, and means for maintaining the air through which the sound travels in homogeneity, substantially as described.

9. The combination with a source of sound, of a rece1ver, means for causlng the concentration of a portion of the sound wave at a predetermined position with respect to the receiver, and means for regulating the temperature of the air through which the sound travels in order to maintain it in ho-r mogeneity, substantially as described.

10. The combination with a source of sound, of a receiver, means for causing the concentration of a predetermined selected portion of the sound wave at a predetermined position with respect to the receiver, and means for regulating the temperature of the air-through which the sound travels in order to maintain it in homogeneity, substantially as described.

11. The combination with a source of sound, of a receiver, means for causing the;

concentration of a portion of the sound wave at a position between the source of sound and the receiver, and means for regulating the temperature of the air through which the sound travels in order to maintain it in homogeneity, substantially as described.

12. The combination with a source of sound, ofareceiver, means for causing the concentration of a predetermined selected portion of the sound wave at a position between the source of sound and the receiver, 1

and means for regulating the tem erature of the air through which the soun travels causing the combination in order to maintain it in homogeneity, substantially as described.

13. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of portions of the sound waves at a predetermined position with respect to the receiver, and means for regulating the temperature of the air through which the sound travels in order to maintain it in homogeneity, substantially as described.

14. The combination with a plurality of sources of sound, of a receiver, means for and concentration of predetermined selected portions of the sound Waves at a predetermined position with respect to the rgceiver, and means for regulating the temperature of the air through which the sound travels in order to maintain it in homogeneity, substantially as described.

15. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of portions of the sound waves at a position between the sources of sound and the receiver, and means for regulating the temperature of the air through which the sound travels in order to maintain it in homogene ity, substantially as described.

16. The combination with a plurality of sources of sound, of a receiver, means for causing the combination and concentration of predetermined selected portions of the sound Waves at a position between the sources of sound and the receiver, and means for regulating the temperature of the air through which the sound travels in order to'maintain it in homogeneity, sub stantially as described.

17. The combination with a chamber, of a source of sound within the chamber, a receiver located in one of the walls of the chamber, and means for causing the concentration of a portion of the sound wave at a predetermined position with respect to the receiver, substantially as described.

18. The combination with a chamber, of

/ a source of sound within the chamber, a remined ceiver located in one of the walls of the chamber, and means for causing the concentration of a portion of the sound wave at a predetermined position with respect to the receiver within the chamber, substantially as described.

19. The combination with a chamber, of a plurality of sources of sound within the chamber, a receiver located in one of the walls of the chamber, and means for causing the combination and concentration of portions 'of the sound waves at a predeterposition with respect to the receiver, substantially as described. 20. The combination with a chamber, of a plurality of sources of sound within the chamber, a receiver located in one of the walls of the chamber, and means for causing the combination and concentration of portions of the sound waves at a predetermined position with respect to the receiver within the chamber, scribed.

21. The combination with a chamber, of a sourceof sound within the chamber, a receiver located in one of the walls of the chamber, means for causing the concentration of a portion of the sound wave at a predetermined position with respect to the receiver, and means for maintaining the air within the chamber in homogeneity, substantially as described.

22. The combination. with a chamber, of a source of sound within the chamber, a receiver located in one of the walls of the chamber, means for causing the concentration of a portion of the sound wave at a predetermined position with respect to the receiver within the chamber, and means for maintaining the air within the chamber in homogeneity, substantially as described.

23. The combination with a chamber, of a source of sound within the chamber, a receiver located in one of the walls of the chamber, means for causing the concentrasubstantially -as detion of a portion of the sound wave at a I predetermined position with respect to the receiver, and means for regulating the temperature of the air Within the chamber in order to maintain it in homogeneity, substantially as described.

24. The combination with a chamber, of a source of sound within the chamber, a sound-absorbing surface within the chamber, a receiver located in one of the walls of the chamber, and a deflecting surface within the chamber positioned to cause the concentration of a portion of the sound wave at a predetermined position with respect to the receiver, substantially as described.

25. The combination with a chamber, of a source of sound within the chamber, a sound-absorbing surface within the chamber, a receiver located in one of the walls of for causing the concentration of of the sound wave at a predetermined position with respect to the receiver, substantially as described.

27. The combination with a chamber having hot-air ducts in its floor and cold-air a portion within the chamber, a receiver located in one of the walls ofthe chamber, and means ducts in its ceiling, of asource of sound within the chamber and beyond the range of action of the air ducts, a receiver located in one of the walls of the chamber and beyond the range of action of the air ducts,

and means for causing the concentration of a portion of the sound wave at a predetermined position with respect tothe receiver,

substantially as described.

28. The combination with a chamber having hot-air ducts in its floor and cold-air ducts in its ceiling, of a source of sound at one end of and within the chamber, a receiver located in the wall of the chamber. opposite the source of sound, andmeans for causing the concentration of a portion of the sound wave at .a predetermined position with respect to the receiver, substantially as described.

29. The combination with a chamber substantially ovoidal in form, of a source of sound within the chamber, a receiver located in one of the walls of the chamber, andmeans for causing the concentration of a .portion of the sound wave at a predetermined position with respect to the receiver, substantially as described.

30. The combination with a chamber substantially ovoigal in form, of a source of sound located ithin and at the smaller end of the chamber, a receiver located in, the wall at the larger end of the chamber, and means for causing the concentration of a portion of the sound wave, at a predetermined position with respect to the receiver, substantially as described. 31. The combination with a chamber having hot-air ducts in its floor and cold-air ducts in its ceiling, of a source of sound at one end of the chamber, and a receiver located at the other end of the chamber, substantially as described.

32; The combination with a chamber having hot-air ducts in its floor and cold-air ducts in its ceiling, of a source of sound .at

one end of the chamber, a receiver located at the other end of the chamber, and means for causing the concentration of a portion of the sound wave at a predetermined position with respect to the receiver, substantially as described.

33. The combination with a source of sound, of a receiver, and means for maintaining the air between the source of sound and the receiver in homogeneity, substan tially as described.

34. The combination with a chamber, of a source of sound. within the chamber, ,a receiver within the chamber, and means for maintaining the air between the source of sound and the receiver in homogeneity, sub stantially .as described.

35. The combination with a chamber, of a source of sound within the chamber, a receiver located in one of the walls of the chamber, means for causing the concentration of a portionof the sound wave at a predetermined position with respect to the receiver, and lighting means for the chamber located beyond the range of action of the concentrating means, substantially as described.

36. The combination with a chamber substantially ovoidal in form, of a source of sound within and at the smaller end of the chamber, a receiver located in the wall at the larger end of the chamber, means for causing the concentration ufa ortion of the sound wave at a predetermined position with respect to the receiver, and lighting means located at opposite sides of the chamber, substantially as described.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

SYDNEY I. PRESCOTT.

Witnesses FRANK B. MIDDLETON, Jr., ETHEL M. WHITEHEAD. 

